Instantaneous rate based cooperative MAC protocol for wireless ad hoc networks

In this work, we propose an instantaneous rate based cooperative medium access control (MAC) protocol (termed as IrcMAC) and compare its performance gain over the existing cooperative MAC protocols under heavy load and fast fading conditions. CoopMAC I protocol, proposed in [5] which selects either direct path or relay path based on rate comparison to enhance average throughput and delay, performs worse under fading conditions due to lower direct path or relay path reliability. UtdMAC protocol, proposed in [8], performs better than CoopMAC I due to improved transmission reliability provided by the back up relay path, however, it uses relay path only as a secondary backup path. Our proposed IrcMAC protocol makes use of channel coherence time and estimates instantaneous signal-to-noise ratio (snr(t)) of source-to-relay, relay-to-destination and source-to-destination links; to reliably select between relay path or direct path for enhanced throughput and delay performances. Simulation results clearly show that IrcMAC significantly outperforms the existing CoopMAC I and the UtdMAC protocols in wireless ad hoc network.